Acridine orange staining method to reveal the characteristic features of an intravascular threadlike structure

In situ microextraction method to determine the viscosity of biofluid in threadlike structures on the surfaces of mammalian organs

We report a method to measure the viscosity of microL volumes of biofluid obtained from threadlike structures (NTSs) on the surfaces of mammalian (rabbit) internal organs. The fluid was mechanically microextracted in situ from NTSs on the organ surfaces by a glass capillary connected to an extractor. From the Brownian motion of the 0.8+/-0.1microm diameter granules in the extracted fluid, the fluid viscosity was determined to be 1.4+/-0.1mPa s at room temperature. This viscosity is comparable to the viscosity of rabbit blood plasma.

Measurement of flow speed in the channels of novel threadlike structures on the surfaces of mammalian organs

There have been several reports on novel threadlike structures (NTSs) on the surfaces of the internal organs of rats and rabbits since their first observation by Bonghan Kim in 1963. To confirm this novel circulatory function, it is necessary to observe the flow of liquid through the NTS as well as the structurally corroborating channels in the NTS. In this article, we report on the measurement of the flow speed of Alcian blue solution in the NTSs on the organ surfaces of rabbits, and we present electron microscopic images depicting the cribrous cross-section with channels. The speed was measured as 0.3 +/- 0.1 mm/s, and the flow distance was up to 12 cm. The flow was unidirectional, and the phase contrast microscopic images showed that the NTSs were strongly stained with Alcian blue. The ultrastructure of the NTSs revealed by cryo-scanning electron microscopy and high-voltage electron microscopy showed that (1) there were cell-like bodies and globular clumps of matter inside the sinus of the channel with thin strands of segregated zones which is a microscopic evidence of the liquid flow, (2) the sinuses have wall structures surrounded with extracellular matrices of collagenous fibers, and (3) there exists a cribriform structure of sinuses. To understand the mechanism for the circulation, a quantitative analysis of the flow speed has been undertaken applying a simplified windkessel model. In this analysis, it was shown that the liquid flow through the NTSs could be due to peristaltic motion of the NTS itself.

Alcian Blue Staining Method to Visualize Bonghan Threads Inside Large Caliber Lymphatic Vessels And X-Ray Microtomography to Reveal Their Microchannels

BACKGROUND

Novel threadlike structures, so-called Bonghan threads, inside large caliber lymphatic vessels were recently observed by using the Janus Green B staining in the case of rabbits, and by using fluorescent magnetic nanoparticles for rats. They are thought to have channels through which some liquid with abundant hyaluronic acid (HA) flows. In the present work, the authors put forward a hypothesis to test that the Bonghan threads can be visualized in vivo by HA-staining dye, Alcian blue, and that the channels may be revealed by using X-ray microtomography.

METHODS AND RESULTS

Alcain blue was injected into a lymph vessel near the caudal vena cava of a rat to make the Bonghan threads visible. Specimens were stained with YoYo-1 and Masson's trichrome. They were also examined by confocal microscopy and X-ray microtomography. A Bonghan thread was well stained by Alcian blue and was about 50 microm thick and 10-20 times thinner than the surrounding lymphatic vessel. It had a broken line shape, with a distribution of rod-shaped nuclei, which is the characteristic of Bonghan threads in general. Whereas lymphatic vessels are surrounded by a collagenous matrix, Bonghan threads do not contain any collagenous component. X-ray microtomography revealed continuous microchannels inside the Bonghan threads.

CONCLUSIONS

Bonghan threads contain HA abundantly, harbor continuous microchannels, and have characteristic distribution of the rod-shape nuclei. Thus, they are novel anatomical structures with liquid-carrying microchannels.

Use of magnetic nanoparticles to visualize threadlike structures inside lymphatic vessels of rats

A novel application of fluorescent magnetic nanoparticles was made to visualize a new tissue which had not been detectable by using simple stereomicroscopes. This unfamiliar threadlike structure inside the lymphatic vessels of rats was demonstrated in vivo by injecting nanoparticles into lymph nodes and applying magnetic fields on the collecting lymph vessels so that the nanoparticles were taken up by the threadlike structures. Confocal laser scanning microscope images of cryosectioned specimens exhibited that the nanoparticles were absorbed more strongly by the threadlike structure than by the lymphatic vessels. Further examination using a transmission electron microscope revealed that the nanoparticles had been captured between the reticular fibers in the extracellular matrix of the threadlike structures. The emerging technology of nanoparticles not only allows the extremely elusive threadlike structures to be visualized but also is expected to provide a magnetically controllable means to investigate their physiological functions.

Electron microscopic study of novel threadlike structures on the surfaces of mammalian organs

The ultrastructures of novel threadlike structures (NTSs) and corpuscles on the surfaces of internal organs of rats were investigated using electron microscopy. The samples were studied in situ by using a stereomicroscope and were taken for further morphological analysis. Scanning electron microscope (SEM) images revealed a bundle structure of threadlike tissue, which was composed of several 10-micro m-thick subducts. The surfaces of the corpuscles were rather coarse and fenestrated. The corpuscles had cucumber-like shapes with an average length of about 2 mm and a thickness of about 400 micro m. Transmission electron microscope (TEM) images disclosed disordered collagen fibers, which formed the extracellular matrix of the threadlike tissue, and immune-function cells, like macrophages, mast cells, and eosinophils. Sinuses of various diameters, which were thought to be cross-sections of the lumens of the subducts, were observed in the TEM, cryo-SEM and focused-ion-beam SEM images. These SEM images were obtained for the first time to reveal the detailed structure of the NTSs that were only recently discovered.

Feulgen reaction study of novel threadlike structures (Bonghan ducts) on the surfaces of mammalian organs

Threadlike structures on the surfaces of internal organs, which are thought to be part of the Bonghan duct system, were first reported about 40 years ago, but have been largely ignored since then. Recently, they were rediscovered, and in this study we discuss the Feulgen reaction that specifically stains DNA in order to identify these structures on the surface of rabbit livers as part of the Bonghan system. The distribution, shapes, and sizes of their nuclei are found to be similar to those of intravascular threadlike structures. The endothelial nuclei are rod-shaped, 10-20 mum long, and aligned in a broken-line striped fashion. The threadlike structure consists of a bundle of several subducts, which is a characteristic feature of Bonghan ducts and distinguishes them morphologically from lymphatic vessels. In addition, the Feulgen reaction clearly demonstrates that the subducts pass through a corpuscle, which is usually irregular or oval-shaped and is connected to two or several threadlike structures that form a web on the surfaces of organs. Furthermore, spherical granules of about 1 mum in diameter are detected in the subducts. These granules were well stained by using the Feulgen reaction, which implies that they contain DNA. According to previous reports, a granule is a type of microcell and plays an essential role in the physiology and therapeutic effect of the Bonghan system and acupuncture. This role has yet to be elucidated.

Novel threadlike structures (Bonghan ducts) inside lymphatic vessels of rabbits visualized with a Janus Green B staining method

A staining method has been developed for in situ and in vivo observation of a threadlike tissue afloat inside the lymphatic vessels of rabbits without adherence to the vessel wall. The existence of this novel structure was not noticed previously because it is extremely difficult to detect it by microscopic inspection of lymphatic vessels. We have found a method that utilizes Janus Green B (JGB), which stained heavily the novel structure. The tissue was studied by confocal laser scanning microscopy (CLSM), light microscopy, and cryoscanning electron microscopy (cryo-SEM). The CLSM image obtained by acridine orange staining of the novel tissue revealed its characteristic nuclei distribution: rod-shaped nuclei of 10-20 microm length aligned in a broken-line/striped fashion. Hematoxylin and eosin staining revealed the threadlike structure passing through a lymphatic valve as histologically distinct from lymphatic vessels and valves. The cryo-SEM image showed the threadlike structure inside a collapsed lymphatic vessel. There were spherical globular structures observable inside sinuses in a rapidly frozen sample, which suggests liquid flowing through the longitudinal ductules in the threadlike structure. The specific staining of the JGB suggests that these threadlike structures inside lymphatic vessels have a high density of mitochondria in their cells and/or nerve-like properties, either of which may provide important clues to their physiological function.